Fuel delivery issues

[upnorth]

Boat has been giving me a few problems the last few times out and the last time was really bad. I have an 87 70 horse Evinrude with a 20 gallon in hull tank.

It seems like it is just not getting enough gas from the tank. It doesn't really want pump the bulb up firm like normal and will run for a while and die or just not idle for any length of time.

I changed the bulb and new lines and didn't really get any better. I even had some issues getting gas into the bulb. Got it going and again not really a firm bulb. It would run but not idle for any length of time. I popped the hood and watched the filter and it didn't seem to want to fill up. Pulled it apart and cleaned it and replace a broken clamp. Tried it again to good. I added a few more gallons of gas to the tank figuring the gauge may be way off, no diff, pulled the gas cap off to rule out not breathing no diff.

Took the line off the fitting for the inboard tank and stuck the line in a gas jug and lo and behold running as normal.

So it would seem there is an issue with the inboard tank and probably not the fuel pump which is only a couple years old anyway. I am thinking of dragging the compressor out and blowing the line to the tank out with the hopes of there being some sort of blockage in the line and or a filter in the tank or something.

Anyone have any other suggestions???

I did take a peak at where the line goes and I would need to pull the floor etc if I have to replace the line.

[theoilman]

What kind of gas do you run? Have you ever used any with ethanol?

The older fiberglass in hull tanks are subject to problems with the ethanol that can leach something from the fiberglass into the gas, then cause plugging in the lines and filters. (Note, the newer fiberglass doesn't have the same problems.)

[upnorth]

Straight pump gas 87 octane which is recommended for the motor. I have tried premium and there was really no difference.

[boatfixer]

Sounds to me like the pick up tube in the tank may be the problem. Either plugged (restricting flow) or may have pinholes (sucking air).

[upnorth]

OK, how do I troubleshoot that? Pull the floor and pull it out of the tank?

[boatfixer]

You say you disconnected from the built in tank, stuck it in a jug and it worked fine? I would hook it up to a 6 gallon tank and run it underload as normal just to be sure, but ya, the next thing is to remove the pick up tube and inspect it.

[upnorth]

OK I do have a portable tank I can test it with. Ugh, pulling up the floor don't sound like a whole lot of fun

[upnorth]

Well dug out the compressor and blew the lines from the motor back into the tank out and it seems to have done the trick. Had it out on the water today and ran like normal. Must have been something in the lines or the pick up tube plugged.

[Surface Tension]

boatfixer nailed it.

The fitting on your tank that you were able to get at to remove the fuel line is the same fitting you take off to replace the drop tube inside the tank. On the end of that drop tube is a brass valve. It will let fuel out only when it is being drawn by the bulb or fuel pump. Those plug and corrode. Also its weight keeps the drop tube on the bottom of the tank.